1. Field of the invention
The present invention relates to a novel multilinear charge transfer array structure, as well as to its analysis process.
2. Description of the prior art
Multilinear arrays generally comprise N rows of P photosensitive detectors, such as photodiodes, each row successively receiving the radiation to be detected, and a device making it possible to summate in synchronism with the movement, the informations collected on the detectors on the same row, said device being known as time delay integration or TDI.
FIG. 1 diagrammatically shows the first detectors D.sub.1, D.sub.2, . . . D.sub.N of each row, as well as a device performing the TDI function for these N detectors. An arrow running from left to right also indicates the movement direction of the array in front of the object or body 1 emitting the radiation to be detected. For the in phase summation of the collected information, it is necessary to supply thereto time delays of times value T, 2T, . . . NT, in which T is the passage time of the object or body emitting the radiation, in front of each detector. T is also the integration time of each detector. FIG. 1 diagrammatically shows that a time delay T is supplied to the information from detector D.sub.1 before being supplied to a summator, a time delay 2T is supplied to the information from detector D.sub.2 and so on.
In the case of multilinear arrays of this type, the integration time is multiplied by N. However, the reading noise is summated in a quadratic manner, so that there is a gain on the signal to noise ratio equal to .sqroot.N. Thus, this type of photosensitive array is of particular interest for capturing X-ray pictures, because it makes it possible to reduce the X-ray dose used for the same exposure time.
In addition, this type of photosensitive array is also used in the analysis of documents by contact in order to improve the resolution in the paper movement or advance direction.